1. Field of the Invention
The present invention relates to a sealing means or a gasket strip of elastic resilient material having a uniform cross-section, for sealing the gap between first and second elements having substantially equidistant sealing surfaces, said gasket substantially non-slidingly engaging said sealing surfaces during relative assembly movement of said elements in a direction substantially parallel to the sealing surfaces and perpendicular to the gasket strip whereas portions of the gasket slidingly engage each other to allow the assembly movement, the gasket comprising a main sealing body providing a resilient sealing pressure when deformed and at least one further body connected to the main sealing body and defining a closed cavity containing a lubricant, said further body being formed by walls having a thickness that is small compared with that of the main sealing body and being positioned between said main sealing body and the sealing surface of one of the elements when the elements have been assembled.
2. Prior Art Statement
U.S. Pat. No. 4,299,399 discloses an annular gasket for sealing the annular gap between two assembled tubular elements such as concrete pipes. The gasket includes a main sealing body and a thin-walled jacket which together with the main sealing body defines a closed cavity containing a lubricant. During axial assembly of the two pipes the jacket slides on a sliding surface of the main sealing body and moves beyond the main sealing body to provide a double buffer layer positioned in an axial annular gap between the two pipes axially inside of the main sealing body.
Such a gasket may be provided in a groove in the socket end or the spigot end of each length of pipe. However, this complicates the molding of the pipes. Concrete pipes may be molded in an upright position in a mold comprising a mandrel, an outer mold portion and a hat-shaped bottom ring determining the shape of the socket end of the pipe. To allow the bottom ring to be removed after the concrete is cured, it must be slightly conical. If the groove for the gasket is to be provided in the socket, the gasket may be mounted on the bottom ring to determine the shape of the groove. However, for obtaining a compression of the gasket between the substantially coaxial sealing surfaces on the spigot and socket ends, the gasket has to protrude radially from the groove into the opening of the socket. This can be achieved to some extent if the gasket is provided with a rigid hoop, reducing the outer diameter of the gasket and compressing it on the bottom ring. Still, if the compression is large, the mounting of the gasket on the bottom ring will be complicated.
As an additional measure and provided a relatively long assembly movement is acceptable and sufficient gap space is available axially inside the main sealing body of the gasket, the thickness of the gasket can be increased during assembly by increasing the thickness of the jacket wall from the end thereof initially positioned in the gap between the main sealing body and the sealing surface on the spigot end. The long sockets necessary for gradually achieving the increased thickness by this approach, are, however, frequently undesirable. Further, such a gasket requires a high degree of control over the length of the assembly movement.